Hydraulic fracturing is a technology that has evolved into a mature, complex level The use of hydraulic fracturing is critical to the economical production of hydrocarbons; and is a significant portion of the well-development cost. Despite the progress, it is still not fully understood, and can be interpreted poorly. Although the physical laws governing fracturing are known, the constant emergence of new mechanisms indicates that the basic physics incorporated into models has not been sufficient to model a fracture fully.
The reasons for the uncertainty surrounding the fracturing process are clear. The Earth is a complex, discontinuous medium, and historically there has been limited technology for observing or inferring fracturing results. Nothing can be done about the complexity of typical reservoirs in the Earth, and one can expect that difficulties with complexity will increase as more marginal reservoirs are exploited. On the other hand, diagnostic capabilities continue to improve and technology is reaching the point where fracture diagnostics can be applied by the average producer in problem situations, in new fields, or for validation of new fracturing techniques.
Furthermore, as operators continue to work in difficult, complex lithologies, it becomes clear that stimulation problems cannot be solved without some diagnostic data from which judicious decisions can be made. Diagnostics cost money, but trial-and-error approaches often cost more money and can result in lost wells. Decisions on well spacing, field layout, sand concentrations and volumes, number of zones that can be stimulated in one treatment, optimum perforation schedule, and many other operational parameters can be made correctly if the proper diagnostic information is available in a timely manner.
Recent developments in the use of electromagnetic sensing to monitor wafer fronts during water injection of conventional oil formations offer the possibility of applying electromagnetic sensing to monitor fracture growth during hydraulic fracturing operations. The concept would be to deploy a distributed or multi-point electromagnetic sensing system into a hydraulic fracturing wellbore before hydraulic fracturing begins. And then to possibly use fracturing fluids with different resistivity properties as well as the use of particles that have desirable properties (e.g. coated electromagnetic particles). The change in electromagnetic field and/or reservoir properties could then potentially be used to monitor fracturing operations in real time to maximize reservoir production performance.
There is a need then to develop these new capabilities for monitoring of the progress of hydraulic fracturing operations.